Water-soluble PVA bag containing free-flowing and non-caking highly concentrated plant growth regulator composition

ABSTRACT

The present invention provides hygroscopic plant growth regulator formulations in solid forms comprising at least 95% active agent, and associated methods of making the powders and tablets. The most preferred formulation uses an effective amount of an N,N-dimethyl-piperidinium salt.

This is a divisional of application Ser. No. 08/095,122, filed Jul. 20,1993 now U.S. Pat. No. 5,468,720.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to methods for making flowable, highlyconcentrated powders and tablets of hygroscopic plant growth regulatorcompounds, and more specifically to processes to dry mepiquat chlorideaqueous solutions to form flowable highly concentrated solid products.

2. Background of the Prior Art

Plant growth regulators affect the physiology of plant growth andinfluence the natural rhythm of a plant. More specifically, plant growthregulators may, for example, reduce plant height, stimulate seedgermination, induce flowering, promote or inhibit fog, darken leafcoloring, minimize lodging of cereals, slow grass growth on lawns,reduce boll rot and provide better boll retention in cotton.

Plant growth regulators may be applied to plants in a variety of methodsincluding different formulations. Of these various methods, use ofliquid and dry compositions are the most common. The particularformulation desired and resulting efficacy enhancement will greatlydepend upon the species to be treated, environmental conditions, thegeographical area and the climatology of the area at the time oftreatment.

The plant growth regulator, known trivially as mepiquat chloride, isgenerally used to control various aspects of cotton boll growth. See,for example, Khafaga, Angew. Botanik 57, 257-265 (1983); Sawan et al.,J. Agronomy & Plant Science, 154, 120-128 (1985); U.S. Pat. Nos.3,905,798 and 4,447,255.

Mepiquat chloride is used as a plant growth regulator in agriculture.Mepiquat chloride has a high water solubility of more than 600 g/L. Themelting point is 223° C. The substance is very hygroscopic when exposedto humid air. The substance is very hygroscopic, readily absorbingmoisture from humid air, so much so, that the dry powder can turn toliquid when exposed to ambient humid air. During storage, the solidmepiquat chloride readily cakes and sticks to container surfaces, evenat low residual water contents of less than 0.5%.

These properties make it extremely difficult to dry mepiquat chloride.In conventional spray dryers, the material is very difficult to dry. Itmust be atomized extremely finely to reduce the moisture to a suitablelevel and even then it retains too much water to dry practically. Theproduct remains sticky and adheres to the walls of the dryer and thedryer ducts and cyclones, eventually plugging the ducts and cyclones.Furthermore, powder from such a process, because it is so fine, flowspoorly out of the dryer, and upon storage in a drum, is renderedunflowable due to caking.

Solid forms of plant growth regulators offer a number of key advantages,including convenience, increased stability and shelf life, as well asreduced packaging, storage and shipping costs. Additionally, there isthe possibility of future government regulation requiring solid forms ofagricultural products in order to reduce handling of contaminatedpackaging of these products during field application and duringdisposal. These dry flowable plant growth regulating compounds would besafer for the farmer to use and dispose of, and also result in a smallervolume of hazardous waste being produced.

There is a need for dry, flowable, highly concentrated powder and tabletformulations of hygroscopic plant growth regulators.

SUMMARY OF THE INVENTION

Surprisingly, a free-flowing, non-caking solid mepiquat chlorideformulation can be achieved by mixing the solid hygroscopic plant growthregulator with finely divided, highly absorptive inerts. In suchmixtures, concentrations of the plant growth regulator of up to about 99percent by weight are achievable. When the mixtures of the invention aredirectly applied in a spray tank, the plant growth regulator dissolvesinstantly in the water without residues.

The preferred plant growth regulators of the present inventions includethe group consisting of 1,1-dimethyl-3,4-dehydropiperidinium bromide,4-chloro-1,1-dimethyl piperidinium bromide,1,1-dimethylhexahydropyridazinium bromide, and 1,1-dimethylpiperidiniumchloride, also known as mepiquat chloride.

It is an object of the present invention to provide an agriculturallyacceptable hygroscopic plant growth regulator formulation in a solidform.

It is a further object of the present invention to provide methods ofmaking the solid form of hygroscopic plant growth regulator compositionsof the present invention.

It is another object of the present invention to provide anagriculturally acceptable hygroscopic plant growth regulator formulationin the form of a tablet.

It is a further object of the present invention to provide methods ofmaking the dry, flowable tablet form of hygroscopic plant growthregulator compositions of the present invention.

These and other objects of the present invention will be more fullyunderstood from the following description of the invention.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 illustrates a spray dryer used in a method of the presentinvention.

FIG. 2 illustrates a double drum dryer used in a method of the presentinvention.

FIG. 3 illustrates a batch vacuum dryer used in a method of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As used herein, the term "agriculturally acceptable" includesagricultural, industrial and residential use.

As used herein, "plant growth regulator (s)" (hereinafter abbreviated as"PGR") or "regulation" includes the following plant responses:inhibition of cell elongation, for example reduction in stem height andinternodal distance., strengthening of the stem wall, thus increasingthe resistance to lodging; compact growth in ornamentals for theeconomic production of improved quality plants; promotion of betterfruiting; increasing the number of ovaries with a view to stepping upyield; promotion of senescence of the formation of tissue enabling fruitto absciss; defoliation of nursery and ornamental bushes and trees formail-order business in the fall; defoliation of trees to interruptparasitic chains of infection; hastening of ripening, with a view toprogramming the harvest by reducing the harvest to one to two pickingsand interrupting the food-chain for injurious insects.

As used herein, PGR formulation of the present invention may be used toform both package and tank mix compositions.

The present preferred invention comprises PGR compositions comprising anagriculturally and plant growth regulating effective amount of ahygroscopic PGR, and more preferably, an N,N-dimethylpiperidinium saltin a dry flowable highly concentrated powder.

Preferred PGRs include salts of the formula: ##STR1## where R is methylor ethyl; X is the anion of an inorganic or organic, but not phytotoxicacid, preferably bromide or chloride, and A is a chain of 4 or 5methylene groups, which chain may be substituted by chloro, bromo,methyl, chloromethyl, bromomethyl, hydroxymethyl, and methylene, orwhich chain containing one or two double bonds, or A is the chain--(CH₂)_(n) --NH--, where n is 3 or 4, disclosed in U.S. Pat. No.3,905,798 and hereby incorporated by reference.

Preferred specific examples of PGRs include1,1-dimethyl-3,4-dehydro-piperidinium bromide,4-chloro-1,1-dimethyl-piperidinium bromide,1,1-dimethylhexahydropyridazinium bromide and 1,1-dimethyl-piperidiniumchloride. The most preferred plant growth regulator is1,1-dimethyl-piperidinium chloride, also known asN,N-dimethylpiperidinium chloride or mepiquat chloride. This product iscommercially available under the registered trademark Pix® (BASF AG,Germany).

For convenience of description, mepiquat chloride will be used. However,the methods described apply equally to other hygroscopic PGRs.

In a preferred embodiment, silica is injected in the inlet air stream ofa spray dryer at a controlled rate.

A spray dryer of the type illustrated in FIG. 1 may be used. As can beshown from FIG. 1, the aqueous PGR feed solution is agitated in a feedtank (2) and fed through a line (4) via a feed pump (6) into the spraydryer unit (8). The aqueous PGR feed solution is introduced into thespray dryer unit by an atomizing means (10). An inlet air heating means(12) provides heat to the dryer at a temperature of about 150 to about250 degrees °C.

A flow aid such as silica is stored in a feed hopper (14) and injectedinto the spray dryer unit (8) via a screw feeder (16) through a line byan air eductor (18). The silica adheres to the forming droplets orpartially dried particles formed by the aqueous mepiquat chloride feedsolution in the vicinity of the atomizer (10) and reduces or eliminatesthe tendency of the partially dried mepiquat chloride particles fromsticking to the spray drying unit walls (20, 22), the ducts (24), andthe cyclone (26). The silica also renders the powder more flowable,eliminating caking in the drum even when stored for long periods of timeprovided the drum excludes ambient moist air. The flowing powder is thensuitable for commercial tabletting or for filling water soluble bags.

The rate at which the aqueous PGR feed solution is fed into the spraydryer unit is not critical and is dependent upon the size of the spraydryer used. This rate is easily determined by those skilled in the art.

A preferred method dries the mepiquat chloride solution with a doubledrum dryer as illustrated in FIG. 2. The double drum dryer has a pair ofhollow, rotating drums (28, 30) whose surfaces are scraped by arespective knife (32). High pressure steam is introduced to the interiorof the drums and mepiquat chloride solution added continuously via afeed line (34) to the nip between the drums (36). The drums turn towardone another, by means of a conveyor, for example 38 depositing a portionof the liquid, boiling mepiquat chloride solution on the drum surface(28, 30) where boiling is initiated. Upon further rotation, the thinfilm of mepiquat chloride's water boils off into the vapor hood (40) anda solid film remains that is scraped by sharp knives (32) from theturning drum surface (28, 30). The material is then collected and theflow aid is added to it to improve flowability and impart anti-cakingproperties prior to tabletting or filling water soluble bags.

A preferred embodiment of the drying process utilizes a batch vacuumdryer with chopping blades which can also be described as a mechanicalfluid bed. The most preferred batch vacuum dryer is a Littleford® type(or Lodige) vacuum dryer, as illustrated in FIG. 3.

As is seen from FIG. 3, the vacuum dryer unit (50) consists of doublejacket (42, 44). Inside the double jacket is a hollow rotating shaft(46) with attached plough shaped mixing elements (48).

Aqueous PGR feed solution is fed via a line (50) into the vacuum dryerunit (52). Steam or hot water (54) is fed via a line (56) into a jacket(42) which surrounds the vacuum dryer unit (52), and optionally throughthe hollow rotating shaft (46). Agitating means (56) in the interior ofthe vacuum dryer unit (52) agitates the aqueous PGR feed solution. Avacuum means (58), which may be a pump or vacuum jet unit is introducedinto and applied to the vacuum dryer unit (52). The vacuum and appliedjacket heat causes the evaporation of the water from the aqueous PGRfeed solution. The evaporated water boils up, passes through a bagcollector means (60), and is recovered by a condenser (62) and collectedin a condensate tank (64).

When a sufficient amount of water has been evaporated, a paste begins toform. Mixing elements (48) are used to divide the paste, breaking it up,and bringing the interior moisture to the surface so as to expose it tothe vacuum to increase the drying rate. As the material solidifies, thechopping means breaks the material into small particles to maintain thehigh drying rate.

A free-flowing, non-caking solid mepiquat chloride formulation can beachieved by mixing the solid mepiquat chloride with a finely divided,highly absorptive inert flow aid such as silica. The addition of silicaor other flow aid renders the powder flowable and non-caking, andsuitable for tabletting or filling water soluble bags. The flow aid isintroduced manually or mechanically through a port on or near the top ofthe drying chamber.

All three drying processes use silica or other flow aid to improveflowability and prevent caking. These inert additives include any formof silica including fumed silicas, precipitated silicas, aluminumsilicates, magnesium silicates, and the like, zeolites, bentoinites,montmorillonites, and attapulgites and mixtures thereof. The mostpreferred silica is commercially available as Sipernat® 50S.

The weight of silica per weight of mepiquat chloride in all of thesedrying processes is about 0.2:100 to 3:100, and more particularly, about2:100.

Optionally, to further improve flowability, reduce sticking tendancy orcaking, or to increase the dissolution rate, binders, fillers, and/ordisintegrants can be dissolved in the feed solution before drying.Suitable binders, fillers, and/or disintegrants include water-solublecellulose derivatives, cellulose derivatives, carboxymethyl cellulose,hydroxypropyl methylcellulose, water soluble gums such as gum arabic,gum tragacanth, alginates, gelatin, and polyvinylpyrollidone,cross-linked polyvinylpyrollidone, microcrystalline cellulose, modifiedstarches such as sodium carboxymethyl starch, and mixtures thereof.

Other suitable fillers, binders, and/or disintegrants include any watersoluble starch, corn syrup, dextrin or pregelatinized starch which is atleast partially soluble in water at ambient temperature. For example,there can be used as a binder the pregelatinized, modified andstabilized waxy maize starch which is marketed by the National Starchand Chemical Corporation under the trade name Instant Celar Gel. Inaddition, pregelatinized corn starch marketing by the Hubinger Companyunder the trade name OK Pre-Gel can be used. Other binders suitable foruse are pregelatinized food starch, refined from tapioca and marketedunder the trade name Instant Gel; stable, modified amylopectin marketedunder the trade name Kosol; a low viscosity tapioca dextrin marketedunder the trade name Crystal Gum; dextrinized corn starch marketed underthe trade name Purity Glaze; maltodextrin marketed under the trade nameMaltrin, such as M040 by Grain Processing Corporation.

All of the above-described powders, with and without fillers, binders,and/or disintegrating agents can then be tabletted or filled into watersoluble bags. Unexpectedly, the high potency powders which contain onlythe hygroscopic PGR active material and silica flow aid, tablet withoutaid of binders, fillers, and/or disintegrants, or lubricants on acommercial tablet press. The tablets formed are of commercial quality,having reproducible weight, sufficient tablet strength, and acceptablesolubility. Water absorbance is minimal provided that the tablets aremade in a dehumidified room. The tablets can be dissolved and passedthrough a 50 mesh screen such as that found on spray equipment withoutresidue.

While the ratios of the concentrations of the various components of thepresent invention hereinafter suggested, those skilled in the art willrecognize that minor variations may be necessary to accommodateparticular characteristics of acceptable plant growth regulators whichmay be employed in this invention.

In general, the formulations of the present invention contain from about0.1 to about 99.8%, and preferably from about 95 to about 99% by weightof active ingredient.

Typically, for a plant growth regulator concentrate of the presentinvention, the concentration of regulator active ingredient will be atleast 0.0125 pints/acre.

In such mixtures, concentrations of mepiquat chloride up to about 99percent by weight are achievable. When the mixtures of the invention aredirectly applied in a spray tank, the mepiquat chloride dissolvesinstantly in the water and this spray solution passes a 50 mesh screenof the spray equipment without residues.

The tablets can be manufactured by compressing the mixtures on tabletmachines. Also for tabletting, other inert ingredients likedisintegrants, binders, fillers, and/or disintegrants, wetting agents orlubricants can be blended with the PGR mixture. (Optionally, the wettingagents and lubricants can be incorporated by addition in the dryingstep--either into the PGR liquid solution before drying, or can be addedwith the inert flow aid during drying.)

When the tablets are dropped into the water of the spray tank, themepiquat chloride is quickly dissolved and this spray solution passes a50 mesh screen of the spray equipment without residues.

In addition to the above-described components, the compositions of thepresent invention may also include other ingredients or adjuvantscommonly employed in the art.

Examples of such ingredients include drift control agents, defoamingagents, preservatives, surfactants, fertilizers, phytotoxicants,herbicides, pesticides, insecticides, fungicides, wetting agents,adherents, nematocides, bactericides, trace elements, synergists,antidotes, mixtures thereof and other such adjuvants well known in theplant growth regulator art.

However, it is preferred to employ the compositions of the presentinvention along with sequential treatments with these other componentsfor optimal effect.

The compositions of the present invention may be applied to plants. Theapplication of liquid and particulate solid plant growth regulatorcompositions to above ground portions of plants may be carried out byconventional methods, for example, boom and hand application, includingsprayers or dusters. The composition may be applied aerially as a spray,if desired. The mixtures of the present invention are preferably used inthe form of aqueous solutions. The mixtures are applied in aconventional manner, for example, by spraying, atomizing, watering ordisinfecting seed.

The forms of application depend entirely on the purpose for which thecompositions are being used. In any event, they should ensure a finedistribution of the active ingredients in the composition.

The above plant growth regulator formulation may then be dispersed inwater and sprayed onto plants according to the method of the presentinvention.

Powders, dusts and broadcasting agents may be prepared by mixing orgrinding the active ingredients with a solid carrier.

Granules, for example, coated, impregnated or homogeneous granules, maybe prepared by bonding the active ingredients to solid carriers.Examples of solid carriers are mineral earths such as silicic acid,silica gels, silicates, talc, kaolin, Attaclay, limestone, lime, chalk,bole, loess, clay, dolomite, diatomaceous earth, calcium sulfate,magnesium sulfate, magnesium oxide, ground plastics, fertilizers such asammonium sulfate, ammonium phosphate, ammonium nitrate, and ureas, andvegetable products such as grain flours, bark meal, wood meal, andnutshell meal, cellulosic powders, and the like.

The action of the compositions of the present invention are optimal evenat low application rates. For a given plant growth regulatorcomposition, the skilled artisan will readily arrive at a compositionhaving the optimum ratio of the ingredients by routine experimentation.

The compositions of this invention may be prepared, for example, byadding, in any order, the various components of the composition of thepresent invention. For example, one may start with a commercialformulation of mepiquat chloride, which is an aqueous concentratecontaining 0.35 pounds per gallon of mepiquat chloride (4.2%) by weight.Thereafter, in any order, one mixes suitable amounts of any optionaladjuvants or ingredients.

The following examples serve to illustrate the invention and should inno way be construed as limiting the scope thereof.

EXAMPLES Example 1--Formulation

An aqueous solution of mepiquat chloride was dried to give a solidmepiquat chloride with a water content of 0.2%. This product was notfree flowing and caked in a sealed, tight container after 2 days ofstorage at room temperature.

Directly after drying, 198 g solid mepiquat chloride were mixed with 2 gof Aerosil® 200 in a laboratory mixer to give a homogeneous mixture.After storage in a sealed container for 1 month at room temperature and50° C., there was no caking. The mixture remained free flowing. Twentygrams of the mixture were poured into a laboratory spray tank filledwith 1 gallon tap water at room temperature. The mepiquat chloridedissolved completely within 1 minute. There was no residue on a 100 meshscreen of the laboratory spray tank.

Example 2--Water Soluble Bag

One hundred grams of the mixture described in Example 1 were packagedusing a water soluble film (Monosol® M7030). This water soluble bag wasdropped into a spray tank filled with 25 gal. tap water at roomtemperature. The water was circulated through a 50 mesh screen. Themepiquat chloride and the film of the bag dissolved completely within 10minutes. These was no residue on the 50 mesh screen.

Example 3--Tablet Formulation

Ninety-five grams of the mixture described in Example 1 and 5 gDivergan® F were blended in a laboratory mixer. A 15 g tablet, 21/2 in.(5.7 cm) diameter, was made with a hand operated hydraulic press. Thetablet was dropped into a spray tank with tap water at room temperature.The tablet broke up completely and the mepiquat chloride dissolvedwithin 10 minutes. There was no residue on the 50 mesh screen of thespray tank.

Example 4--Formulation

Directly after drying as described in Example 1, 294 g solid mepiquatchloride were mixed with 6 g Sipernat® 50 S in a laboratory mixer togive a homogeneous mixture. After storage in a sealed container for 1month at room temperature and 50° C., there was no caking. The mixtureremained free flowing.

Twenty grams of the mixture were poured into a laboratory spray tankfilled with 1 gal. tap water at room temperature. The mepiquat chloridedissolved completely within 1 minute. There was no residue on the 100mesh screen of the laboratory spray tank.

Example 5--Water Soluble Bag

One hundred grams of the mixture described in Example 4 were packagedusing a water soluble film (Mono Sol® M8532). This water soluble bag wasdropped into a spray tank filled with 25 gal. tap water at roomtemperature. The water was circulated through a 100 mesh screen. Themepiquat chloride and the film dissolved completely within 10 minutes.These was no residue on the 100 mesh screen.

Example 6--Tablet Formulation

Using the mixture of Examples 4, 20 g tablets, 21/2 in. (5.7 cm)diameter, were made with a hand operated hydraulic press. Five tabletswere dropped into a spray tank filled with 25 gal. tap water at roomtemperature. The tablets broke up completely and the mepiquat chloridedissolved within 12 minutes. There was no residue on the 100 mesh screenof the spray tank.

Example 7--Formulation

A 600 g/L solution of mepiquat chloride was placed in an agitated,jacketed, spray dryer feed tank and heated to 65° C. with temperedwater. The heated solution was pumped at 125 g/min to an atomizing wheelrotating at about 17,000 rpm in a Niro Utility spray dryer. Silica(Sipernat 50S) from a loss-in-weight screwfeeder was injected via an aireductor into the air plenum to mix with the heated air entering theplenum. The silica was fed at a rate of 4% based on the dry basis feedrate of the mepiquat chloride solution. The silica/air mixture, at 200°C., then entered the drying chamber, intermixing with the dropletsformed by the atomizer. The resultant outlet temperature is about 140°C. On drying the powder exits the drying chamber does not adhere to thewalls of the spray dryer, the ducting, or the cyclone separator. Thepowder remains flowable in a polyethylene bag packed in a sealed plasticdrum.

The resulting powder was flowable, had a moisture content of 0.25%, abulk density of 0.29 g/ml untapped, 0.38 g/ml tapped, and an ash contentof about 2%. The powder assayed at about 97% mepiquat chloride.

Example 8

Steam at 105 psig was introduced to a lab scale double drum dryer andthe rolls rotated at about 5 rpm. Mepiquat chloride liquid was fed froma reservoir to the nip of the rolls at a rate of about 36 g/minute. Thematerial adhered to the rolls and the moisture was evaporated while thedrums rotated. The solid film was scraped off the rolls by a blade andcollected. Material collected without silica rapidly caked. Materialthat was collected and mixed with about 2% (Sipernat 50S) silica did notcake and was flowable. The moisture content was about 1.2% in theresultant powder, with a density of 0.25 g/ml untapped and 0.35 g/mltapped.

Example 9

To a 130 liter Littleford "mechanical fluid bed" dryer (Model FKM-130with chopping blade), 171.6 lbs of mepiquat chloride 600 g/L aqueoussolution was charged. The agitator plough was started at 155 rpm, and 15psig steam introduced to the jacket. A vacuum was pulled with a vacuumpump, maintaining 600 mm Hg at the pump. The evaporated vapors passedthrough a bag filter and were condensed using a cold glycol/watermixture on the shell side of a condenser. The resulting condensate wascollected in a receiver. As evaporation continued, the amperage drawn bythe plough motor began to rise. The chopper blades were turned on, andthe drying completed. During this time the steam pressure on the jacketwas progressively increased to drive off the water from the formingpaste. As more water was removed, the paste turned to solid, the choppergreatly increasing the rate of drying by dividing moist material andexposing the interior moisture to the vacuum and hot dryer walls. Whenwater was no longer being removed, the dried solid was cooled byapplying cool water to the jacked of the apparatus. Approximately 2% ofsilica was then added to the material and allowed to blend. When thismixing operation was complete, the finished product was discharged to adrum.

The resulting free flowing powder was composed of particles ranging fromapproximately 5 to 60 microns in diameter, with a moisture of about0.08%, and bulk density of 0.63 untapped and 0.79 tapped, and ashcontent of about 2%. The powder assayed at about 97% mepiquat chloride.There was no detectable mepiquat chloride in the overhead condensate.

Example 10

About 10 pounds of powder made by the method in Example 9 was charged tothe feed hopper of a single station Stokes R excenter tablet presslocated in a low humidity room. The relative humidity of the roomremained about 28% between 70° and 80° F. The press was fitting withtooling to make 2.25 inch diameter tablets. After pressure and sizeadjustments, tablets were made of about 21 grams with good tabletintegrity. Hardnesses, as measured on a RIMAC tester, were 15 to 21 lbsforce. Tablets were found to have picked up less than 0.3% moistureduring this operation.

The tablets had thicknesses of about 0.8 to 0.9 centimeters. The tabletsdissolved under mild agitation in water in about 7 to 9 minutes and theresulting liquid did not deposit any residue when passed through 150micron sieve (100 mesh).

Whereas particular embodiments of the invention have been describedabove for purposes of illustration, it will be appreciated by thoseskilled in the art that numerous variations of the details may be madewithout departing from the invention as described in the appendedclaims.

Example 11

A mepiquat chloride powder prepared by the method of (example 8 for drumdryer) was tabletted in a Carver press. Press pressure was varied at 6to 7 metric tons, 8 to 9 metric tons, and 10 to 11 metric tons fordurations of 1 minute each. The formed tablets, of 2.26 inches indiameter, had thicknesses between 0.24 and 0.26 inches with weights ofbetween 15.3 to 15.6 gms, with breaking strengths between 9 and 22.3 lbsas determined on a modified Chatillon electronic tester, model DFI-50mounted on a model LTC manual test stand. The tablets were dissolved in750 ml of 342 ppm hardness water stirred with a magnetic stirring barand dissolved completely in 0.9 to 4.7 minutes.

Example 12

A mepiquat chloride powder prepared by the method of (example 9 for theLittleford dryer) was tabletted in a Carver press. Press pressure wasvaried at 8 to 9 metric tons, and 10 to 11 metric tons for durations of1 minute each. The formed tablets, of 2.26 inches in diameter, hadthicknesses between 0.24 and 0.26 inches with weights of between 15.3 to15.7 gms, with breaking strengths between 17 and 32 lbs as determined ona modified Chatillon electronic tester, model DFI-50 mounted on a modelLTC manual test stand. The tablets were dissolved in 750 ml of 342 ppmhardness water stirred with a magnetic stirring bar and dissolvedcompletely in 4.4 to 5.8 minutes.

Example 13

A mepiquat chloride powder prepared by the method of (example 7 for thespray dryer) was tabletted in a Carver press. Press pressure was variedat 6 to 7 metric tons, 8 to 9 metric tons, and 10 to 11 metric tons fordurations of 1 minute each. The formed tablets, of 2.26 inches indiameter, had thicknesses between 0.23 and 0.28 inches with weights ofbetween 14.4 to 15.7 gms, with breaking strengths between 16.5 and 55lbs as determined on a modified Chatillon electronic tester, modelDFI-50 mounted on a model LTC manual test stand. The tablets weredissolved in 750 ml of 342 ppm hardness water stirred with a magneticstirring bar and dissolved completely in 3.8 to 4.8 minutes.

Whereas particular embodiments of the invention have been describedabove for purposes of illustration, it will be appreciated by thoseskilled in the art that numerous variations of the details may be madewithout departing from the invention as described in the appendedclaims.

What is claimed is:
 1. A water-soluble PVA bag which contains a dry,flowable powder of a hygroscopic plant growth regulator which comprisesa mixture of (i) a solid particulate consisting essentially of at least95% by weight of said hygroscopic plant growth regulator, and (ii) aneffective amount between 0.2 to 3 parts by weight per 100 parts byweight of the plant growth regulator of an inert flow aid sufficient toinhibit hygroscopicity of said plant growth regulator such that saidpowder remains free-flowing and non-caking in said PVA bag.
 2. The PVAbag of claim 1, wherein said inert flow aid is selected from the groupconsisting of silicas, fumed silicas precipitated silicas, aluminumsilicates, magnesium silicates, zeolites, bentonites, montmorillonites,attapulgites, and mixtures thereof.
 3. The PVA bag of claim 1, whereinsaid plant growth regulator is mepiquat chloride.
 4. The PVA bag ofclaim 1, wherein the dry, flowable powder comprises fillers, bindersand/or disintegrants.
 5. The PVA bag of claim 4, wherein the fillers,binders and/or disintegrants are selected form the group consisting ofwater-soluble cellulose derivatives, cellulose derivatives,carboxymethyl cellulose, hydroxypropyl methylcellulose, water-solubleplant gums, alignates, gelatin, polyvinylpyrolidone, water-solublestarch, corn syrup, dextrin, pregelatinized starch which is at leastpartially soluble in water at ambient temperature, pregelatinized foodstarch, stable modified amylopectin, a low viscosity tapioca dextrin,dextrinized corn starch, maltodextrin microcrystalline cellulose,crosslinked polyvinyl pyrollidone, sodium carboxymethyl starch, andmixtures thereof.
 6. The PVA bag of claim 4, wherein the fillers,binders and/or disintegrants are carboxymethylcellulose.
 7. The PVA bagof claim 4, wherein the fillers, binders and/or disintegrants aredissolved in a hygroscopic plant growth regulator feed solution beforedrying.
 8. The PVA bag of claim 4, wherein the fillers, binders and/ordisintegrants are present in an amount of about 0.1 to about 99.7%. 9.The PVA bag of claim 4, wherein the fillers, binders and/ordisintegrants are present in an amount such that a ratio of the plantgrowth regulator to the fillers, binders and/or disintegrants is betweenabout 0.1:99.7 to 99.7:0.1.
 10. The PVA bag as in claim 1, wherein theplant growth regulator is an N,N-dimethyl-piperdinium salt.
 11. The PVAas in claim 10, wherein the plant growth regulator is selected form thegroup consisting of 1,1-dimethyl-3,4-dehydropiperidinium bromide,4-chloro-1,1-dimethylpiperidinium bromide,1,1-dimethyl-hexahydropyridazinium bromide, and 1,1-dimethylpiperidiniumchloride.
 12. The PVA bag as in claim 10, wherein the plant growthregulator is 1,1-dimethylpiperidinium chloride.